To improve fuel economy, fuel delivery to an engine in a hybrid or conventional powertrain vehicle may be deactivated during vehicle deceleration. The vehicle engine, which delivers torque to the wheels, does not produce propulsion torque when fuel is deactivated. During fuel deactivation, the vehicle engine may be back driven by the wheels.
Traditionally, fuel is deactivated when the vehicle is decelerated. While this system improves fuel economy, it may also cause degraded drivability. When the vehicle undergoes short periods of deceleration and acceleration, fuel is deactivated and reactivated in succession. Rapid intervals of fuel deactivation and activation may cause driveline disturbance and degraded drivability.
When the vehicle is decelerated after a transmission up-shift, fuel deactivation in the traditional system may occur and the transmission may be immediately down-shifted. A transmission up-shift followed by an immediate fuel deactivation and transmission down-shift cause driveline disturbance and degraded drivability.